Meter to Inches: significant figures

[Glenn Lawton <lawtonglenn@gsmai.com>]

OK, so James Marriott sends me a few pages out of the Fifth
edition (1993) of Mechanical Measurements by Beckwith, T.G.
clearing up some of the differences in meter to inch conversions.

It is six pages long, but here are a few clips:

"...In 1866 , the Revised Statutes of the United States, Section 3569,
added the stipulation that 'It shall be lawful throughout the United States
of America to employ the weights and measures of the metric system'...
and  "1 meter (m) = 39.37 inches (in.) (exactly)."

"...On October 20th, 1983, the Seventeenth General Conference on Weights
and Measures defined...The meter is the length of a path traveled by light
in vacuum during a time interval of 1/299,792,458 of a second"

"...The convenient relation 1 in. = 2.54 cm (exactly)...through adoption
of the SI system, became official for all length conversions"

"...This problem might be serious, were it not for the fact that geodetic
distances and small mechanical displacements seldom need to be compared...
In 1959, The U.S. government defined separately the U.S. survey foot (12/39.37 m)
and the international foot (12x2.54 cm). The survey foot is still used
with U.S. geodetic data and U.S. statute miles."


Therefore:

International SI units (1983)  1 m = 39.3700787 in

U.S. geodetic data (1959)      1 m = 39.3700000 in

Mr. Marriott was incorrect in calling me "chronologically challenged", as
the conversion I used is more recent, and accepted worldwide, and used in
the US for all but geodetic measurements.

I also claim that "...a foot of snow..." is more accurately defined as a
"...small mechanical displacement..." than a "...geodetic distance..."

Big Smile
Glenn